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The Young Spinoza on Scepticism, Truth, and Method

Published online by Cambridge University Press:  22 October 2019

Valtteri Viljanen
School of History, Culture and Arts Studies, University of Turku, Turku, Finland
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This paper offers a new interpretation of the young Spinoza’s method of distinguishing the true ideas from the false, which shows that his answer to the sceptic is not a failure. This method combines analysis and synthesis as follows: if we can say of the object of an idea (a) which simple things underlie it, (b) how it can be constructed out of simple elements, and (c) what properties it has after it has been produced, doubt concerning the object simply makes no sense. The paper also suggests a way in which this methodology connects to the ontology of the Ethics.

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1. Introduction

“As the light makes both itself and the darkness plain, so truth is the standard [norma] both of itself and of the false” (E2p43s);Footnote 1 or as Spinoza says in his correspondence, “truth is the sign [index] of itself and of the false” (Ep76; G IV, 320). Again, “truth requires no sign [signo]” (TIE § 36; G II, 15).Footnote 2 Given the brevity of these memorable claims, it is understandable that, for instance, Edwin Curley (Reference Curley1988, 65) has estimated that Spinoza “does not take Cartesian scepticism seriously.”Footnote 3 After a short exposition of Spinoza’s discussion of the nature of adequate ideas in the Treatise on the Emendation of the Intellect, Jonathan Bennett comments (Reference Bennett1984, 176): “It is not a good discussion. Fortunately, the interest in scepticism which prevails in the Emendation is almost absent from the Ethics.” Harold Joachim (Reference Joachim1940, 197) laments that “my attempt to extract from Spinoza’s exposition in the Treatise his principal contentions in regard to doubt, and to weave out of them a complete restatement of his theory, has ended in an open admission of failure… . For the theory, when examined in detail, shows itself to be in fact no single, coherent theory at all.”Footnote 4

However, Spinoza’s relationship to scepticism has also received more positive attention. Many different kinds of answers to the sceptical challenge can be, and have been, found in his works. I believe that Willis Doney’s estimation is basically correct (Reference Doney1971, 617): “In the Ethics, Spinoza is not expressly concerned with scepticism and the possibility envisaged by Descartes that clear and distinct ideas or conceptions may not be true. There is reason for this, as he was of the opinion that, if as in the Ethics we proceed in our thinking in the right order, doubt will not arise.” More recently, Michael Della Rocca (Reference Della Rocca2007) argued that Spinoza’s argument against scepticism is grounded on his commitment to the principle of sufficient reason and the denial of inexplicable bifurcations (e.g., that between the clarity and distinctness of an idea and certainty) it entails. The latest interpretation of Spinoza’s answer to the sceptic which focuses on the Ethics is by Dominik Perler (Reference Perler and Rocca2018), according to whom the masterpiece contains a kind of combination of the coherence and correspondence theories of truth which shows that the sceptic’s position is untenable. Finally, if we take a look at the proposition of the Ethics most directly focusing on scepticism (E2p43), we find its demonstration’s central claim: “[h]e who has a true idea at the same time knows that he has a true idea, and cannot doubt the truth of the thing,” to rely on God’s omniscience and on the theory of the ideas of ideas. As such, the argument is to a notable degree embedded in the mature Spinoza’s philosophical system.

In this paper, I examine the way in which the Spinoza of the Treatise on the Emendation of the Intellect thinks his view of truth and method allows him to dispel sceptical doubts. I believe it is warranted to focus on this early work not only because it offers its author’s most extensive treatment of scepticism but also because its arguments can be evaluated without taking a stand on the large-scale philosophical system Spinoza later develops. Even though Spinoza’s line of argument decisively differs from the famous, or notorious, argument of the Third Meditation,Footnote 5 I will show that his position is deeply entrenched in certain aspects of Cartesian thought expressed in the early Regulae. Now, Spinoza’s debt to Descartes of the Regulae certainly has drawn some notable attention in the scholarship;Footnote 6 however, I believe that there is still more to be said about the way in which Spinoza’s Treatise is influenced by his predecessor’s early work. Discerning the specific way in which the Treatise is in line with the Regulae will prove to be singularly helpful in arriving at the core of my paper: an interpretation of the young Spinoza’s theory of distinguishing true ideas from the false. This aspect of Spinoza’s thought has recently received welcome renewed attention. Although I find some of the presented claims correct—which is, of course, only to be expected—to my knowledge my interpretation is unprecedented in the literature and original in its basic orientation.Footnote 7 Precisely this new interpretation enables me to defend Spinoza against those interpreters who have claimed that his answer to the sceptic is an awkward failure. Moreover, my account allows me to throw light on how the methodology of the Treatise is connected to the ontology of the Ethics.

The paper will unfold as follows. In section 2, I explain what, for Spinoza, is the object of adequate ideas; knowing this is the indispensable first step in discerning what truth and falsity are about. In section 3, I argue that the core of Spinoza’s method of distinguishing the true ideas from the false is formed by a specific combination of analysis and synthesis. Finally, in section 4, I show how, by this method, Spinoza answers the sceptical challenge—here, perhaps somewhat boldly, I find it helpful to compare his mindset to the way in which Kant thinks about spatial cognition—and suggest a way in which Spinoza’s answer to the sceptic connects to his ontology.

2. Spinoza on the object of adequate ideas

In the Ethics, Spinoza famously makes a three-tiered distinction between different types of knowledge. First, there are ideas of imagination formed through the senses and from signs, and inadequate in character. The second kind of knowledge, reason, is something we obtain from “common notions and adequate ideas of the properties of things” (E2p40s2). Finally, there is the famed intuitive knowledge, which “proceeds from an adequate idea of the formal essence of certain attributes of God to the adequate knowledge of the [NS: formal] essence of things” (E2p40s2). As is well known, this highest kind of knowledge has been found to be something of a mystery. Here it suffices to observe that it concerns the essences of things that follow from the essence of God-or-Nature, whereas reason concerns (merely) the properties of things.

The classification in the Treatise is similar in designating the ideas we have from reports, signs, and sense experience as perceptions of lower levels. The second highest kind of knowledge is delineated in a way that differs from the Ethics:

There is the Perception that we have when the essence of a thing is inferred from another thing, but not adequately. This happens, either when we infer the cause from some effect, or when something is inferred from some universal, which some property always accompanies.

(TIE § 19; G II, 10)

Spinoza is somewhat ambivalent about the status of this type of knowledge. Although he states that “we can, in a sense, say that we have an idea of the thing, and that we can also make inferences without danger of error,” he adds: “But still, it will not through itself be the means of our reaching our perfection” (TIE § 28; G II, 13). Only the highest mode of knowledge, “the Perception we have when a thing is perceived through its essence alone, or through knowledge of its proximate cause” (TIE § 19; G II, 10), “comprehends the adequate essence of the thing and is without danger of error. For that reason, it is what we must chiefly use” (TIE § 29; G II, 13). Thus, even though this classification significantly differs from the one presented in the Ethics, it should be kept in mind that also here Spinoza emphasizes the role of essences in adequate knowledge formation. Clear and distinct ideas are first and foremost about the essences of things.

What, then, does Spinoza understand by essence? The basic answer to this question seems to remain unaltered through his philosophical career.Footnote 8 An early and succinct formulation runs:

Understand the definite nature, by which the thing is what it is, and which cannot in any way be taken from it without destroying it, as it belongs to the essence of a mountain to have a valley, or the essence of a mountain is that it has a valley.

(KV I.1; C, 61; G I, 15)

The famous definition of the Ethics is more complex but still in line with the aforesaid:

I say that to the essence of any thing belongs that which, being given, the thing is [NS: also] necessarily posited and which, being taken away, the thing is necessarily [NS: also] taken away; or that without which the thing can neither be nor be conceived, and which can neither be nor be conceived without the thing.


I take this to mean that the essence is that what makes a thing what it is—individuates it. Essences have other tasks as well; most notably, they are the sources of causal efficacy (see E1p34, 1p36, 3p7d)—but as far as I can see, these tasks are not relevant to understanding the epistemological discussions of the Treatise.

It is not, I believe, interpretatively contentious to say that for Spinoza, an essence is a feature of reality that determines a specific way of being, which forms the very core of a thing, or constitutes it. The primary cognitive path to essences goes through definitions. A definition expresses an essence; it is a complete account of the essence of a thing, or as Spinoza also says, it is the concept of the thing (TIE § 96; G II, 35). Here Spinoza is very much thinking along the traditional lines, comparable, for instance, to Aquinas when he states, “a thing is intelligible only through its definition and essence” (SW, 35). In a nutshell, for Spinoza the proper objects of ideas concerning things are essences that determine the basic character of the being of those things, and they can be conceived through definitions.Footnote 9

3. Spinoza on truth and falsity of ideas

It can roughly be said that according to the young Spinoza there are two different ways of forming knowledge: the intellectual way of examining the essences of things and the imaginative way of forming ideas of things in their present state of existence, in which state they affect us.Footnote 10 Despite the fact that ideas of imagination are very useful for practical life, they are uncertain and epistemically inadequate, for they are not about the basic, constitutive, or essential features of things (TIE §§ 19–20, 26–27; G II, 10–11, 12–13). The main goal of the rather convoluted methodological discussion of the Treatise is to discern the nature of adequate knowledge formation based on essences. In keeping with the view that truth is its own sign or standard, Spinoza straightforwardly says that we do have a true idea and that by examining it we can discern the nature of our understanding and the right standard of truth. In other words, the method is reflexive knowledge, an idea of an idea (TIE §§ 37–38; G II, 15–16). But what exactly does this mean? How can we be sure that we have a true idea? One does not have to be a sceptic to be puzzled about this.

The answer Spinoza gives to this question builds on Cartesian theses, but not on those Descartes presents in the Third Meditation. Spinoza argues as follows. We have ideas,Footnote 11 because our minds can form them.Footnote 12 Analogous to the way in which our hands—with which we can work on different kind of materials and make efficient tools—can be regarded as tools given to us by nature, the inborn power of our mind (to form ideas) can be regarded as an inborn tool (TIE § 30–31; G II, 13–14). We can direct our mind toward an idea and focus on the constitutive features of its object—in other words, on its essence. To take an example given by Spinoza, a circle can be defined as the figure generated when one end of a line is kept fixed and the other is moved (TIE § 96; G II, 35).Footnote 13 A very different kind of example—one that has proven very important to the philosophical tradition—would be that of a chimera, an entity definable as an animal with a lion’s head, a goat’s body, and a snake as the tail. Our idea of the former is true, of the latter false. But how can we know this?

The following passage, which to my mind has received too little attention in the literature, outlines the way in which this problem can be solved:

[W]hen the mind attends to a fictitious thing which is false by its very nature, so that it considers it carefully, and understands it, and deduces from it in good order the things to be deduced, it will easily bring its falsity to light. And if the fictitious thing is true by its nature, then when the mind attends to it, so that it understands it, and begins to deduce from it in good order the things that follow from it, it will proceed successfully, without any interruption—just as we have seen that, from the false fiction just mentioned, the intellect immediately applies itself to show its absurdity, and the other things deduced from that.

(TIE § 61; G II, 24; emphasis added)

I will later return to some crucial parts of this passage, but we can begin by observing that sometimes the consideration of an idea is literally a very simple affair. According to Spinoza, such things as extension and motion are essentially completely simple, and ideas about them can only be clear and distinct. The reason for this is that things like these “will have to become known, not in part, but either as a whole or not at all” (TIE § 63; G II, 24). Here Spinoza thinks exactly like Descartes in the Regulae, who elaborates this line of thought in Rule XII as follows:Footnote 14

[S]ince we are concerned here with things only in so far as they are perceived by the intellect, we term “simple” only those things which we know so clearly and distinctly that they cannot be divided by the mind into others which are more distinctly known. Shape, extension and motion, etc. are of this sort; all the rest we conceive to be in a sense composed out of these.

(CSM I, 44; emphasis added)

[T]hese simple natures are all self-evident and never contain any falsity… . [I]t is evident that we are mistaken if we ever judge that we lack complete knowledge of any one of these simple natures. For if we have even the slightest grasp of it in our mind—which we surely must have, on the assumption that we are making a judgement about it—it must follow that we have complete knowledge of it. Otherwise it could not be said to be simple, but a composite[.]

(CSM I, 45; emphasis added)

Ideas of simple things and their essences thus form an epistemically solid starting point for both Descartes and Spinoza early in their career.Footnote 15 This kind of ideas do not contain anything but one uniform thing, and so either one grasps them clearly and distinctly or not at all, which is methodologically crucial.

What about complex things? After all, we are most interested in the truth of the ideas we have of them. The key point is that both Descartes and the young Spinoza think that they are composed of simple things (CSM I, 44; TIE § 68 [G II, 26]). Spinoza stresses that “if, in thought, we divide a thing that is composed of many things into all its most simple parts, and attend to each of these separately, all confusion will disappear” (TIE § 64; G II, 24). He does not illustrate what he means by this, or how this is supposed to happen, but I believe that the following example built from the materials offered by the Treatise captures what he has in mind. Think about a sphere. It can be constructed by rotating a circle around its diameter.Footnote 16 Now motion is something completely simple, but the same cannot be said of the circle, for it presupposes a certain process of generation: Spinoza describes it as the figure produced by keeping one end of a line fixed and moving the other (TIE § 96; G II, 35). Once again, motion is something simple in a way that a line is not; so how do we obtain a line? By moving a point rectilinearly in extension (TIE § 108; G II, 39). In this way we realize that the sphere can be constructed out of, and has as its basis, three completely simple things: extension, point, and motion. Of course, the same applies to the circle I mentioned earlier: it is just a thing less complex than the sphere. Evidently, the Galileo-Cartesian conception of nature underpins Spinoza’s conviction that this kind of geometrical analysis is in principle applicable to all corporeal things, regardless of their level of complexity.Footnote 17

But could not a chimera, too, be in principle analyzable into extension and other simple things? Could it not be just a very complex body which has features of all of those animals we call lions, goats, and snakes? Spinoza does not offer us a direct answer to this question, but one can be extracted from what he says in the Treatise. The illustration concerning the sphere does not tell us only of what simple things the complex thing ultimately consists; it also clearly designates the connections that obtain between the different elements. It thus explains how a complex thing can be produced from simpler things: for instance a sphere can be constructed by moving first a point in extension and then the line that results, and finally by rotating the circle thus produced.Footnote 18 Spinoza notes that when the mind forms the concept of a thing, it sees “together the means and causes, how and why such a thing was done” (TIE § 62; G II, 24; emphasis added). Moreover,

if someone proceeds rightly, by investigating [first] those things which ought to be investigated first, with no interruption in the connection of things,Footnote 19 and knows how to define problems precisely, … he will never have anything but the most certain ideas[.]

(TIE § 80; G II, 30; emphasis added)

Spinoza notes that sometimes one hears highly incredible things, for instance “that trees speak, that men are changed in a moment into stones and into springs” (TIE § 58; G II, 22) and so on. Spinoza’s response to this kind of reports can be characterized broadly as follows: if we carefully consider how and why things like these would occur, we notice that we cannot form a clear and distinct idea of the connections that would have to be involved any more than we can have a clear and distinct idea of the unification of a square and a circle (TIE § 64; G II, 24–25).Footnote 20 Thus the fact that there can be no clarificatory account to be given of how to get from simple things to a chimera shows that we are dealing with a feigned entity of which we cannot form a true idea.Footnote 21 I believe that Spinoza refers precisely to this in the passage cited earlier when he indicates that the mind is interrupted when it considers a falsely feigned idea and what follows from it (TIE § 61; G II, 23–24). In other words, a traditionally defined chimera contains complex ideas combined in a fashion arguably not realizable within Galileo-Cartesian nature—moreover, there is no guarantee that features such as fire-breathing lion’s head are analyzable into such simple things as motion and extension.Footnote 22 Given this, the idea of a chimera is false, because in it confused ideas are combined in an unintelligible way.Footnote 23 It may thus be said to be not only confused but altogether absurd,Footnote 24 which is why it is not surprising to find Spinoza stating that a chimera’s “nature implies that it would be contradictory for it to exist” (TIE § 54; G II, 20). In a similar vein, it holds for the human mind that once we have formed an idea of its essence, it is impossible to think of a mind that is square (TIE § 59; G II, 23).

As already the illustration presented above shows, our idea of a sphere is, for its part, true: its object can be analyzed into simple things or parts, of which we can only have clear and distinct ideas and out of which the sphere can be constructed “in good order.” When such a construction occurs, there is a “series of fixed and eternal things” (TIE § 100; G II, 36) Spinoza later invokes. And given that such a construction results in a thing with a definable essence, it is understandable that Spinoza says singular things to “depend so intimately, and (so to speak) essentially, on the fixed things that they can neither be nor be conceived without them” (TIE § 101; G II, 37). In this way, the mind can form a true idea of the essence of the sphere—in Spinoza’s idiom, it is an eternal truth (TIE § 54; G II, 20). This is why he famously states,

if some architect conceives a building in an orderly fashion, then although such a building never existed, and even never will exist, still the thought of it is true, and the thought is the same, whether the building exists or not.Footnote 25

(TIE § 69; G II, 26)

A crucial methodological advance has thereby been gained: reflecting on a true idea has shown us what the truth of an idea is and given us the criteria (or the “mark”) of truth—and, in fact, thereby shown us what clarity and distinctness actually are. If the mind can both (1) dismantle (“analyze”) the object of the idea to its simplest constituents and (2) construct (“synthesize”) the object of the idea from those constituents, the idea is clear and distinct and hence true. Footnote 26 This notion of truth builds on the view that we have a direct access to the foundation of all corporeal things, that is to extension or space, and that geometry has revealed the principles by which things are constructible out of (and hence disclosed what is true of) extension, which is why simply focusing on the idea we can find out whether or not it is true.

It must be admitted that this notion of truth is not easy for us to grasp, for it certainly brings the idea and its object close to each other—in a sense identifying them—in a way that is difficult to reconcile with our tendency to think truth as correspondence between (“inner”) ideas and (“outer”) objects. However, Spinoza is not alone in thinking along these lines; on the contrary and perhaps surprisingly, his theory of truth comes close to those of both Descartes and Leibniz. In the Fifth Meditation (CSM II, 44–45), the former famously talks about “true and immutable natures,” such as that of a triangle, of which “various properties can be demonstrated,” and this, according to Descartes, shows that such natures “cannot have been invented” by the meditator; even though things with those natures “may not exist anywhere outside” the meditator, they “still cannot be called nothing”—which has given rise to the still ongoing discussion concerning the ontological status of true and immutable natures.Footnote 27 Perhaps even more importantly, Spinoza’s situation seems in a notable respect analogous to that of Leibniz, whose conceptual containment theory of truth has so often been found most puzzling, for, as Robert Adams (Reference Adams1994, 66) puts it, according to it, “[t]ruth or falsity depends only on the logical structure of the proposition and the internal logical structure of its concepts. In this sense, truth is not a semantical but a purely syntactical property of propositions.” In the next section, I attempt to throw more light on this topic—as difficult as it is important—by doing my best to explicate the way in which Spinoza thinks about this and the relationship between the “intrinsic” and “extrinsic” aspects of ideas.

Before moving on, we should note that more than a specific essence pertains to a complex thing,Footnote 28 namely an array of features that necessarily accompany the thing without constituting it. When we are dealing with a genuine (and properly defined) thing, our intellect can infer all these features and form an overall conception of the being of the thing—a conception in which all the different aspects of its object fit together, necessarily stemming from a common source.Footnote 29 Then, to put things in more technical terms, there is a specific essence/property structure. Discussing the example of the circle, Spinoza says that after we have defined it, all of its properties can be deduced from the definition, for instance “that all the lines drawn from the center to the circumference are equal” (TIE § 96; G II, 35).Footnote 30 Thus of a complex thing it can be truly said not only how the thing can be produced from certain simple things, but also what effects or properties the thing has in virtue of its essence. The end result is a clear and distinct chart of a path or form that being can take. All this helps us understand why Spinoza claims that “a true thought is distinguished from a false one not only by an extrinsic, but chiefly by an intrinsic denomination” (TIE § 69; G II, 26). The notion of intrinsic denomination is certainly one of the thorniest in Spinoza’s epistemology.Footnote 31 However, we are now in the position to see what he means by it, at least as far as extended things are concerned: the intrinsic denomination of a true idea of an extended thing is clarity and distinctness concerning the geometrical features of the thing.Footnote 32

4. Spinoza’s answer to the sceptic

We are now in a position to examine how Spinoza of the Treatise answers to the sceptic. After having presented how differently our mind works when it meditates on true ideas and false ones, Spinoza assures us: “So we ought not to fear in any way that we are [merely] feigning something, if only we perceive the thing clearly and distinctly” (TIE § 62; G II, 24). What he means by this is that if an idea can be grasped with complete clarity and distinctness, it is true, and its object is necessarily what we think it to be. Footnote 33 If for Descartes clarity and distinctness is the mark of truth, for Spinoza clarity, distinctness, and truth seem to be even more closely intertwined: there is no wedge to be driven between clarity and distinctness, and truth.

Generally speaking, it seems that Spinoza is to a notable extent prone to regard scepticism as a form of verbal sophistryFootnote 34 whose charm wears off quite quickly when things are investigated with proper care, so that it can be shown, for instance, that arbitrarily connected words have given rise to a confused idea (for instance of a square soul) (TIE § 58; G II, 22). Indeed, Spinoza’s method of distinguishing true ideas from the false is the crux of his answer to the sceptic: “[D]oubt always arises from the fact that things are investigated without order” (TIE § 80; G II, 30). If we can say of the object of an idea (a) which simple things underlie it, (b) how it can be constructed out of the simple elements, and (c) what properties it has after it has been produced, doubt concerning the object simply makes no sense. Perhaps it could even be said (in a Kantian vein) that being constituted by certain clearly and distinctly discernible geometrical principles is essential for being an external object, and any further sceptical challenge is simply misguided in not having grasped the very nature of being an extended finite thing.

Indeed, I believe it is helpful to compare Spinoza’s way of emphasizing the importance of geometry in discerning the structure of corporeal things—especially what may be called the synthetic move from an essence to propertiesFootnote 35—to the Kant of the Transcendental Aesthetic who claims that “[g]eometry is a science that determines the properties of space synthetically and yet a priori” (KrV B40).Footnote 36 Kant even states that “[t]hus also all geometrical principles, (e.g., that in a triangle two sides together are always greater than the third, … are derived from intuition and indeed derived a priori with apodictic certainty” (KrV A25/B39).Footnote 37 It should be noted that this is a claim about the inner constitution of objects, not the much more famous claim that without space, objects could not be in different places. So, for Spinoza as for Kant, it can be said that being determined by geometrical principles is constitutive of being an extended (external) thing (object),Footnote 38 which, to use Spinoza’s words is “the form of the true” (TIE § 69; G II, 26) of spatial things.Footnote 39 Spinoza is convinced that were someone, even after having been taught about this form of the true, to deny that he knows the truth “then either he will speak contrary to his own consciousness” (TIE § 47; G II, 18) or people like him are so cognitively impaired that “if someone proves something to them, they do not know whether the argument is a proof or not,” ending up granting and denying things completely at random (TIE § 48; G II, 18).

In this way, Spinoza argues for a standard of truth whose formulation does not involve God. God certainly has a central role to play in Spinoza’s epistemology: for our knowledge to be maximally perfect, its object must be the most perfect being—God or Nature—and what follows from God’s essence. In this way, the formation of ideas exactly tracks the order of things that stem from the very core of reality.Footnote 40 If someone were still to insist that we could be misled by a deceiving God, I believe that Spinoza would reply that his method of appraising ideas reveals that this objection is based on a confusion: if we consider a proper idea of God, we see that he can be a deceiver as little as the sum of a triangle’s internal angles can equal something other than two right angles (TIE § 79; G II, 35).Footnote 41 The true idea of God’s veracity is thus acquired by the very same method as is the true idea of the sum of the internal angles of a triangle, or of the equality of the lines drawn from the centre of a circle to its circumference; the reliability of the method does not depend on God.Footnote 42

In fact, I believe that here Spinoza’s geometry-inspired approach pushes him to his most idealist position as it were: by focusing with our intellect on the intrinsic denominations of ideas alone (most notably, on clarity and distinctness concerning the geometrical features of an extended object) we can arrive at indubitable truth. This, however, does not necessarily mean that there is a substantial change in his views from the Treatise to the realism of the Ethics, it is just that the former is an explicitly methodological work, while the latter explains what Spinoza calls his “Philosophy.” Clearly, he thinks that for the purposes of the former, it suffices to show that there is no reason to fear that the ideas we acquire in our rational pursuits, ideas carrying the intrinsic denomination of truth, would nevertheless be false because of a deceiving God.

However, a sceptic may not be convinced by this and object—as some have objected to Kant—that Spinoza has not really parried the main sceptical charge, for by staying within what is revealed to the intellect, he has not yet shown that our ideas, whatever their intrinsic characteristics may be, really correspond to anything outside them. It may thus still be asked, what positive guarantee is there that what Spinoza calls true ideas in virtue of certain intrinsic denominations are not only possible but actual as well—that they also have extrinsic denominations, namely relations to objects that are not merely ways in which our intellect is modified? And even more generally, what ensures that there is such a thing as an external world in the first place? Now, it should be noted that even in the Treatise (§ 69), Spinoza does not deny that true ideas have extrinsic denominations as well, it is just that truth of an idea is discerned chiefly or especially (maxime) by its intrinsic denomination. Intrinsic denomination forms the prime aspect of a true idea,Footnote 43 but there is the extrinsic aspect as well.Footnote 44

To give an account of that extrinsic aspect, Spinoza would, I believe, turn to his Philosophy and delineate as it were the complete account of truth. But how are the Method of the Treatise and the Philosophy of the Ethics related to each other? Given that Spinoza says nothing about this perennially difficult question, no answer can avoid being conjectural. I myself am inclined to suggest the following.Footnote 45 Perhaps Spinoza could maintain that by further developing the method specified above so that it shows how to acquire adequate ideas not only of the essences of things but also of basic ontological distinctions, we can reveal the clear and distinct starting point of philosophy, namely the definitions and axioms of the Ethics (especially in its opening part).Footnote 46 In the end, they open up a route from possibility to actuality, a route that does not start with the idea of God, but with fundamental conceptual distinctions in ontology on which are based claims concerning existents.Footnote 47 The most important of these claims are that there necessarily exists absolutely infinite and self-caused substance outside of which there is nothing (E1p15), a substance that necessarily produces, in virtue of its essence, an infinity of finite things as its properties (E1p16). With regard to extension, it can thus be claimed that all the geometrically describable genuine possibilities are necessarily realized by the very core of God or Nature, and so Spinoza can say such things as “what is contained objectively in the intellect must necessarily be in Nature” (E1p30d).Footnote 48 A properly robust ontology is thus required to explain why a true idea acquirable by intellect not only has its intrinsic but an extrinsic denomination as well.Footnote 49 Now, one may not be convinced by Spinoza’s ontology but the main point for our purposes is that without the correct method, in a rationalism such as Spinoza’s, we would be cognitively lostFootnote 50— unable to systematically grasp the basic intrinsic features of things, and demonstrating anything about the world would not get off the ground.

5. Conclusion

In this paper, I have explicated the young Spinoza’s method of discerning the truth and falsity of ideas. That method represents, I believe, one of the most significant contributions to early modern epistemology, a contribution greatly influenced by Descartes, but nevertheless one that succeeds, to my mind, in providing a further developed rationalistic account of the nature of ideas that combines analysis and synthesis in an ingenious manner. Given this account and the view of corporeal things it offers, Spinoza does have a sophisticated answer to the sceptic; if his discussion of scepticism appears at times laconic, impatient, and even derogatory, this is obviously because he is so convinced of the method he offers.


I would like to thank most of all Arto Repo for many extremely helpful remarks and discussions on the topics of this paper; thanks also to Peter Myrdal for insightful points. I am grateful to Stephan Schmid and Justin Steinberg for thorough written comments on an earlier version of the paper, to the two anonymous referees for constructive criticism, and to the Responsible Editor for excellent linguistic suggestions. I would also like to thank the audiences at the University of Turku, Central European University, and Ghent University.

Financial support.

Research for this article has been financially supported by the Academy of Finland (project number 275583).

Valtteri Viljanen is an Academy of Finland Research Fellow at the University of Turku. He is the author of Spinoza’s Geometry of Power (Cambridge University Press, 2011) and numerous articles on Spinoza.


C = Spinoza, Benedictus de. 1985. The Collected Works of Spinoza Vol. I. Translated and edited by Edwin Curley. Princeton: Princeton University Press.

CSM = Descartes, René. 1985. The Philosophical Writings of Descartes I–II. Translated by John Cottingham, Robert Stoothoff, and Dugald Murdoch. Cambridge: Cambridge University Press.

CSMK = Descartes, René. 1991. The Philosophical Writings of Descartes III. The Correspondence. Translated by John Cottingham, Robert Stoothoff, Dugald Murdoch, and Anthony Kenny. Cambridge: Cambridge University Press.

EW = Hobbes, Thomas. 1839–45. The English Works of Thomas Hobbes I–XI. Edited by William Molesworth. London: John Bohn.

G = Spinoza, Benedictus de. 1925. Spinoza Opera I–IV. Edited by Carl Gebhardt. Heidelberg: Carl Winter.

KrV = Kant, Immanuel. 1998. Critique of Pure Reason. Translated and edited by Paul Guyer and Allen W. Wood. Cambridge: Cambridge University Press.

SW = Thomas Aquinas. 1965. Selected Writings of St. Thomas Aquinas. Translated by Robert P. Goodwin. Upper Saddle River: Prentice Hall.


1 I use Curley’s translations (in C) and the following method in referring to the Ethics (abbreviated as E): app = appendix, d = definition, p = proposition, s = scholium. For instance, “E1p8s2” refers to the second scholium of the eighth proposition in the first part of the Ethics. I abbreviate other works by Spinoza as follows: Ep = Correspondence; KV = Short Treatise on God, Man and His Well-being; TIE = Treatise on the Emendation of the Intellect. A list of additional abbreviations can be found in the references section.

2 Cf. “Truth manifests both itself and falsity” (KV II.15; G I, 79).

3 Cf. “Spinoza did not see scepticism as the spectre haunting European philosophy… . Spinoza’s epistemological dogmatism is probably the furthest removed from scepticism of any of the new philosophies of the seventeenth century” (Popkin Reference Popkin1979, 245).

4 The reasons behind this verdict are not altogether easy to discern. If I understand him correctly, the greatest problem according to Joachim (Reference Joachim1940, 196) is that Spinoza conflates the case of “the man of science or philosopher” with that of “a perceiving or imagining, but unreflecting mind” of “subrational doubt.” However, I have been unable to find textual evidence for this distinction. Another critical point is that Spinoza “overlooks … the positive character of doubt as something that involves “pondering over alternatives” (197); but I see no reason why we should endorse precisely this view of doubt. At any rate, even if Joachim’s critical points were solid, I do not think they license such a sweeping negative conclusion concerning Spinoza’s whole theory. In general, I find Joachim’s strong tendency to read the Ethics back into the Treatise problematic; it is often difficult to see the extent to which his criticisms are based on reading the two works as if they were completely contemporaneous.

5 For an account of the anti-Cartesian aspects in Spinoza’s answer to the sceptic, see Bolton Reference Bolton1985.

6 Already Edwin Curley Reference Curley1994 (C, 4) notes that “the Treatise on the Intellect invites comparison to Descartes’s Regulae,” and Jean-Luc Marion (Reference Marion and Yovel1994, 144–45) draws attention to many parallels between the two works. I would like to thank the anonymous referees for emphasizing this.

7 There are two significant recent accounts of the theory of truth in the Treatise. According to Alan Nelson’s (Reference Nelson and Melamed2015) interpretation, the idea of God is the starting point of the early Spinoza’s theory of truth and any true idea “is clearly and distinctly conceived through God because it is a ‘part’ of the intellect of God” (63). Now the Treatise does display some indications of this line of thought (see esp. TIE § 73; G II, 28), which becomes much more prominent later in the Ethics, but since directly beginning from the (alleged) true idea of God would hardly convince any sceptic, I do not think that this is the approach to take; as John Morrison (Reference Morrison and Melamed2015, 77–78) observes, it also faces some notable textual problems. The other interpretation is by Morrison, who argues that Spinoza’s theory of truth is based on an inborn idea of our own essence, but the most convincing textual evidence for this view is located in the Ethics, not the Treatise (see Morrison Reference Morrison and Melamed2015, 89). Moreover, as I will explain in more detail below (see note Footnote 11), I do not think that we have to commit ourselves to any specific view about what Spinoza means by “a given true idea” (TIE § 38; G II, 16), which is welcome simply because, in fact, Spinoza does not tell us what it is. Of the older interpretations, I believe that the one by Alexandre Matheron should be mentioned; while I agree with his core thesis that “we have to conclude that our true idea, right from the beginning, really involved certainty, all by itself, at its own level” (Matheron Reference Matheron and Yovel1994, 86; for a similar approach, see Sangiacomo Reference Sangiacomo2015, 345), Matheron focuses on how to square what Spinoza of the Treatise says about certainty with the doctrine of ideas of ideas of the Ethics. As far as I can see, Matheron does not discuss my main question concerning truth, what exactly makes an idea true in the first place (“at its own level”)? Finally, I agree with Daniel Schneider (Reference Schneider2016) that Spinoza is an epistemological methodist; what I want to show is how the early Spinoza thinks that we can distinguish the clear and distinct ideas from the obscure and confused.

8 For discussion, see Viljanen Reference Viljanen and Melamed2015.

9 Michael Della Rocca (Reference Della Rocca1996, ch. 5; 2007, 863) and John Morrison (Reference Morrison and Melamed2015, 69–71) also emphasize, albeit on different grounds and in differing ways, the importance Spinoza’s epistemology lays on cognizing essences of things.

10 It is true that Spinoza also examines intellectually the existence of things, but in fact this examination is based on natures (or essences) as well: “I call a thing impossible whose nature implies that it would be contradictory for it to exist; necessary whose nature implies that it would be contradictory for it not to exist; and possible whose existence, by its very nature, does not imply a contradiction—either for it to exist or for it not to exist” (TIE § 53; G II, 19–20).

11 As noted above, Spinoza quite soon says that we have a true idea, which can be used as an inborn tool (TIE § 39; G II, 35), but it is notoriously difficult (to say the least) to understand what exactly he has in mind. For a very helpful survey of different interpretative approaches to this problem, see Nelson Reference Nelson and Melamed2015, 53–56. I think the most cautious interpretative strategy is to remain agnostic concerning the nature of the idea Spinoza has in mind here and begin by discussing ideas in general and then finding out on what grounds some of them can be said to be true.

12 This is not to say that our minds would be completely active in forming ideas, only that it would not be possible to form ideas without some kind of contribution by our minds, which thesis, I take it, is quite uncontroversial. For discussion, see Viljanen Reference Viljanen, Silva and Yrjönsuuri2014.

13 Spinoza shares with Hobbes not only the general preference for genetic definitions (that state how the object can be generated; see esp. De Corpore I.6.13; EW I, 81–82) but this particular example as well, which Hobbes uses in De Corpore I.1.5 (I, 6). For discussion of the connection between Hobbes and Spinoza, see Gueroult Reference Gueroult1974, 482–87 and Mancosu Reference Mancosu1996, 98–99.

14 There is no watertight evidence that Spinoza would have read the Regulae, first published in 1684. However, given how closely the Treatise at times seems to follow what Descartes writes in his early work, it would be astonishing if Spinoza was not familiar with at least its key theses. Moreover, copies of the manuscript circulated in the Dutch Cartesian circles. See Joachim Reference Joachim1940, 95n2, 198n2; Nadler Reference Nadler1999, 166, 371; Nelson Reference Nelson and Melamed2015, 57–58. Indeed, there seems to be nowadays a consensus that Spinoza knew the Regulae rather well; for instance, Jean-Luc Marion (Reference Marion and Yovel1994, 145) submits that Spinoza adopts the idea of simple natures from the Regulae.

15 G. H. R. Parkinson (Reference Parkinson1954, 38) protests that “such simple ideas as motion, quantity, &c., affirm nothing” and are therefore “neither true nor false.” However, this complaint is based on an incorrect understanding of Spinoza’s conception of truth. Now, it is true that there is a long tradition of thought in which affirmation and denial, which were thought to be necessary for truth and falsity, were connected to combination and separation. Thus, in this tradition (represented in the early modern period, e.g., by Arnauld and Nicole’s Port-Royal Logic), truth and falsity imply complexity. But it is uncertain whether Descartes belongs to this tradition, and it should be clear to any reader of Spinoza that he definitely does not. Indeed, he seems to have been one of the first philosophers who clearly saw that affirmation cannot be understood in terms of combining ideas as subjects and predicates. This is why in Spinoza’s view there is no problem in thinking that even a simple idea can involve affirmation.

16 TIE § 72 (G II, 27) reads: “… e.g., to form the concept of a sphere, I feign a cause at will, say that a semicircle is rotated around a center, and that the sphere is, as it were, produced by this rotation. This idea, of course, is true, and even though we may know that no sphere in nature was ever produced in this way, nevertheless, this perception is true, and a very easy way of forming the concept of a sphere.”

17 Spinoza nowhere indicates that this kind of analysis would not apply to all things. Indeed, he seems to have inherited much of the epistemic optimism of his greatest immediate predecessor; Descartes declares in the fifth part of the Discourse on the Method that “reviewing in my mind all the objects that have ever been present to my senses, I venture to say that I have never noticed anything in them which I could not explain quite easily by the principles I had discovered” (CSM I, 144). Now Spinoza does not say that discerning the construction of such a complex thing as, for example, the human body would be outright easy, but he appears to be confident that there is no principled reason to think that such a feat would be out of the reach of his method—not realizable as our knowledge of nature progresses.

18 Thus, the Treatise offers a substantive elaboration of what Descartes only briefly delineates in his Discourse (CSM I, 120), especially of the third rule according to which we should direct our “thoughts in an orderly manner, by beginning with the simplest and most easily known objects in order to ascend little by little, step by step, to knowledge of the most complex, and by supposing some order even among objects that have no natural order of precedence.” Despite the fact that Descartes also emphasizes the model set by geometers, here, as Martial Gueroult (Reference Gueroult1974, 482–86) has argued, Hobbes’s influence is certainly strong: in De Corpore I.1.6, Hobbes illustrates generation by saying that “a line is made by the motion of a point, superficies by the motion of a line” (EW I, 70). Moreover, as Hobbes notes, the division (or resolution) into the simple things can be called the analytic method, and the composition from simple things to complex ones the synthetic method (I, 66–70).

19 As Marion (Reference Marion and Yovel1994, 144n25) notes, Descartes of the Regulae quite often refers to the uninterrupted movement of thought. I find it likely that this is one reason why Spinoza opts for this locution.

20 See also TIE §§ 62, 65; G II, 24, 25.

21 In the Conversation with Burman, Descartes makes essentially the same point: “Even though we can with utmost clarity imagine the head of a lion joined to the body of a goat, or some such thing, it does not therefore follow that they exist, since we do not clearly perceive the link, so to speak, which joins the parts together” (CSMK, 343–44; emphasis added).

22 See TdIE §§ 63–64; G II, 24–25.

23 I believe that Spinoza could also answer along these lines Pierre Bayle’s (Reference Bayle and Popkin1965, 317–18; 320–23) classic challenge that Spinoza has no resources to deny the possibility of such things as demons, ghosts, and hell. For discussion, see Popkin Reference Popkin1979, 247.

24 See TIE § 61; G II, 24.

25 See also Ep9 (C, 194), where Spinoza explains that a definition can be good even if its object does not exist outside the intellect.

26 See note Footnote 18 above. Already, Joachim (Reference Joachim1940, 95) draws some attention to what he calls analysis and “deduction”; more recently, Sangiacomo (Reference Sangiacomo2015, 348) offers a brief discussion of analyzing complex ideas into simple ones, whereas Morrison (Reference Morrison and Melamed2015, 75) notes that Spinoza is committed to the idea that adequate complex ideas are deduced from simple ones (see note Footnote 30 below). However, I have not been able to locate a sustained discussion focusing on the combination of analysis and synthesis as explicated by the present interpretation that underpins the young Spinoza’s theory of truth.

27 See, e.g., Cunning Reference Cunning2003; Doney Reference Doney2005; Carriero Reference Carriero2009, 280–304.

28 Cf. “[T]he many things that are contained in each thing” (TIE § 63; G II, 24).

29 Cf. E3p5.

30 As pointed out above (note Footnote 26), Morrison (Reference Morrison and Melamed2015, 75) lays some emphasis on deducing complex ideas from simple ones; however, in line with his overall interpretative strategy, Morrison’s focus here is on ideas formed by the power of the intellect instead of sense perception. Moreover, given that it is Spinoza’s second criterion for a good definition that (necessary) properties can be deduced from it, I find it surprising that Morrison states that “[a] true idea of x represents x’s essence and perhaps also x’s properties” (Morrison Reference Morrison and Melamed2015, 73; emphasis added).

31 Don Garrett (Reference Garrett1986, Reference Garrett1990) offers the most notable discussions of it to date, and emphasizes that truth is—for Spinoza and Leibniz—an internal characteristic of true ideas.

32 It seems to follow from this that if the mind cannot acquire this kind of clarity and distinctness, the idea is false; and this, I believe, really is the young Spinoza’s position, on which I focus here. It is, however, worth noticing that the monistic framework of the Ethics clearly pushes him to reconsider things: E2p47s (G II, 134) states that “I grant that no one is deceived insofar as he perceives, i.e., I grant that the imaginations of the mind, considered in themselves, involve no error.” This claim is obviously based on E2p33, according to which “[t]here is nothing positive in ideas on account of which they are called false,” for falsity can be neither in nor outside the monistic God or Nature. In other words, Spinoza’s mature philosophy changes the picture somewhat; still, as I understand the key passage of the Ethics (E2p47s; G II, 134), Spinoza does not deny that the mind can perceive “that its idea of a winged horse” is inadequate even when there are no other ideas which exclude “the existence of the same horse.” I cannot see on what else but failing to form a clear and distinct idea of its object could reveal the falsity of such an idea, especially as Spinoza also of the Ethics emphasizes the “intrinsic denominations of a true idea” (E2d4; see also note Footnote 44 below). I discuss the relationship between the methodology of the Treatise and the ontology of the Ethics below.

33 See esp. TIE § 65; G II, 25. Cf. Della Rocca’s (Reference Della Rocca2007) argument for the inextricability of mental intelligibility and truth.

34 See TIE § 77; G II, 29.

35 On this, see Carriero Reference Carriero2009, 298–99, 325, 472.

36 On a similar estimation of the relationship between Descartes and Kant, see Carriero Reference Carriero2009, 292–93, 298–301. It should also be noted that Newman and Nelson (Reference Newman and Nelson1999, 395) argue, to my mind quite convincingly, that in his attitude towards skepticism, Descartes prefigures Kant.

37 Of course, Kant’s and Spinoza’s philosophical motivations differ; Spinoza is not a transcendental idealist. It is geometry-inspired epistemology that motivates his position (for more on this, see below). However, they clearly agree about the importance of the principles of geometry in the constitution of extended objects. In fact, I would rather say that Kant rationalizes sensible intuition (by arguing that it must have a geometrically determinable a priori form) than that Spinoza idealizes extension.

38 As Frederick Beiser helpfully observes: “Kant’s third and final account of the empirical reality of space is mathematical or geometrical. According to this explanation, space has empirical reality because transcendental idealism shows that the axioms and theorems of geometry are necessarily true of appearances. If propositions such as ‘only one straight line lies between two points’ and ‘within two straight lines no space can be enclosed’ are universally and necessarily true, then what appears in space cannot be an arbitrary or private perception, still less an illusion of the imagination. Rather, these appearances will be real in virtue of their universal and necessary structure” (Beiser Reference Beiser2002, 57; the final emphasis added).

39 In line with this, Kant states outright that external things exist as evidently as he himself does (see KrV 1998, A370–71), and Spinoza at least suggests that the fact that things are constituted in a certain way is as evident as is the fact that he is a thinking being (see esp. TIE § 58; G II, 58).

40 See TIE §§ 39–42, 75, 91 (G II, 16–17, 28–29, 34); also consider the famous E2p7.

41 Cf. Garrett Reference Garrett1986, 67, 70–71; Mason Reference Mason1993, 555–56, 561, 563. See also the prolegomenon to Descartes’s “Principles of Philosophy” (G I, 147–49). Even though his answer to the sceptic does not rely on God, it should be kept in mind that Spinoza is completely convinced of the fact that he really has a clear and distinct idea of God from whose nature infinitely many properties necessarily follow; see Ep56 and Ep76 (G IV, 261, 319–20). For the Cartesian background of this thesis, see the Fifth Meditation (CSM II, 44–47). For a reading that seems to regard Descartes as proceeding along similar lines as I see Spinoza to proceed here, see Newman and Nelson Reference Newman and Nelson1999, esp. 384.

42 Cf.: “[I]t is only by using our clear and distinct ideas that any such demonstration [of the claim that all of our knowledge depends upon knowledge of God] can be achieved… . Spinoza concludes via his clear and distinct ideas that his clear and distinct ideas are the idea of an infinite intellect” (Schneider Reference Schneider2016, 596–97).

43 As Schneider (Reference Schneider2016, 591) puts it: “At the most foundational level, a true idea is distinguished from fiction on account of its own intrinsic features.” In the same vein, Morrison (Reference Morrison and Melamed2015, 70) states: “The definitive features of a true idea x are intrinsic to the mind in which that idea is true.” As I understand it, the reference to features intrinsic to the mind is of paramount importance for Morrison’s reading and a move I am not prepared to make; see note Footnote 30 above.

44 An important definition of the Ethics echoes this: “By adequate idea I understand an idea which, insofar as it is considered in itself, without relation to an object, has all the properties, or intrinsic denominations of a true idea. Exp. I say intrinsic to exclude what is extrinsic, namely, the agreement of the idea with its object” (E2d4; see also Ep9; C, 194). Despite this, I do not agree with Marion (Reference Marion and Yovel1994, 149) who argues that the Ethics would abandon and even invert the method of the Treatise.

45 I would like to thank an anonymous referee for pressing this important issue and thereby inviting me to refine and revise my position on the matter.

46 Interestingly enough, Spinoza’s silence concerning the way in which he arrived at his first principles is in keeping with Hobbes’s contention that “[t]he whole method … of demonstration … is synthetical” (De Corpore I.6.12; EW I, 80). Cf. Garrett Reference Garrett1986, 86.

47 In this, E1p7 is the key claim, for it is the first proposition that signals that Spinoza’s definitions and axioms amount to more than empty conceptual considerations: based on them, it can be shown that there necessarily exists a substance.

48 Here I agree with Garrett, who argues that given Spinoza’s necessitarianism, “if an idea possesses enough internal consistency or ‘adequacy’ to show that what it represents is a genuine possibility, it will thereby also show it to be actual” (Garrett Reference Garrett and Yovel1991, 213). Indeed, he explicitly defends the view that “logical necessitarianism would provide Spinoza with a consistent and coherent reconciliation of the internalist and externalist conceptions of truth” (Garrett Reference Garrett1990, 37).

49 Although it is quite difficult to place Spinoza within the contemporary framework formed by the debate between the coherence theories and correspondence theories of truth (for a very helpful account of this difficulty, see Curley Reference Curley1994, esp. 15), at this point it can be noted that the intrinsic denomination of a true idea is in a sense its “internal coherence” feature, while Spinoza’s understanding of the notion of extrinsic denomination corresponds to the notion of correspondence. However, it should be kept in mind that the “coherence” involved in Spinoza’s intrinsic denomination is of a very special kind, and that the “correspondence” involves, and stems from, a very specific kind of ontological theory. For a notable alternative discussion of Spinoza as a coherence and correspondence theorist, according to which the correspondence between the idea and its material object is mainly secured by the parallelism of E2p7, see Perler Reference Perler and Rocca2018.

50 Here I am inspired by the way in which Carriero (Reference Carriero2009, 280–300) delineates Descartes’s reasons for introducing true and immutable natures. For Spinoza as for Descartes, there must be a cognitive route to truth that does not rely on sense experience.


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